Module 17 Flashcards
The annual chronotype switch in voles is due to ____, which is higher in the ____ and lower in the _____
- testosterone
- summer
- winter
What are the two mechanisms that control ultradian rhythms and how do they work?
- circannual clock - same as circadian clock but with a period of 1 year
- endogenous interval timer - activated each year by changes in day length, which is measured by the SCN
What is photoperiodism?
The ability to measure day length
What is the entrainment cue for circannual clocks?
Day length
The hybernation rhythm free-runs if day length is ____
- Kept fixed at 12:12 or 14:10
- Replaced by constant dim light
How does day length affect a mammal’s annual rhythms after hibernation?
Does not affect it during the animal’s refractory period
Sensitivity to short day length occurs in hibernating animals by _____
Midsummer
What does the Syrian hampster do during the short days of winter?
Stops breeding
How do SCN lesions affect annual rhythms?
Does not eliminate annual rhythms, but the animal cannot entrain to the annual cycle of day length
What is the chronobiotic effect?
Administration of melatonin to rats free-running in dim light can cause small phase shifts of entrainment if repeated daily
How does melatonin cause phase shifts in humans?
Evening melatonin causes phase advances and morning melatonin causes phase delays
What are examples of annual rhythms in humans?
- More fertile in spring than fall
- melanonin secretion changes when days are shorter
- seasonal affective disorder
What are symptons of seasonal affective disorder?
- Depression
- Hypersomnia
- Carbohydrate cravings
- Increased body weight
SAD prevalence is higher in the _____ hemisphere
North
How does light affect SAD and which light is most effective?
- Decreases symptoms
- 2,50 lux blue light
